Digital timer

ABSTRACT

A digital timer for monitoring flow time through an orifice of a fluid sample having particles suspended therein. The digital timer includes means for presetting a sample flow time and means for providing an alarm when the flow time is greater than the preset time. The timer further includes means for automatically providing a validating signal to indicate that the apparatus has functioned properly and means for measuring digitally the preset time calibration.

United States Patent Berg 1 1 Nov. 18, 1975 1 1 DIGITAL TIMER 3,636.5491/1972 Berman et a1 235/92 T ll 1. 235 92 PC [76] Inventor: Robert H.Berg, 196 Clinton, 3 657 725 4/1972 I Esta e a Elmhurst, 111. 60126 7 Jh M Th J Primary Examiner osep esz, r. [22] Ffled' 1973 Attorney, Agent,or Firm-Hill, Gross, Simpson, Van [.21] App]. No.: 386,219 Santen,Steadman, Chiara & Simpson Related US. Application Data A I [63]Continuation of Ser. No. 166,766. July 28, 1971, [57] ABSTRACTabandoned.

A digital timer for monitoring flow time through an [52] US. Cl. 235/92T; 235/92 PC; 235/92 R; orifice of a fluid sample having particlessuspended 324/71 CP therein. The digital timer includes means forpreset- [51] Int. Cl. G06M 11/00 ting a sample flow time and means forproviding an [58] Field of Search 235/92 PC, 92 T, 92 PE, alarm when theflow time is greater than the preset 235/92 EA, 92 FL; 324/71 CP;340/239, time. The timer further includes means for automati- 243;73/55, 56 cally providing a validating signal to indicate that theapparatus has functioned properly and means for mea- [56] ReferencesCited suring digitally the preset time calibration.

UNITED STATES PATENTS 6 Cl 3 Dr F, 3,074,266 l/1963 Sadler et al 73/55alms awmg gums I AMPLD/SABLE 22 24 27 Y F; 63 F52 60/60 H2 .90 3/ F81 vDIV/D56 29 9,5 96 [5M IL Li Tf/EESHOLD i a I C/ECU/T I 5W? 1 A 8/ l 37 iA9 44 I 39 mums WHEEL II mam/w sw/rcwmssx cou/vrse 1 fi 4/ L j DIGITALTllMER I y i This is a continuation of application Ser. No. rennet,filed July 28, 1971, and now abandoned. 1

BACKGROUND OF THE INVENTION I use of a microscope or an enlargedmicroscopic projection to visually, monitor obstructions tosample, flowthrough an orifice and accordingly discount the data of an operationwherein such a blockage. occurred. The obvious disadvantage of visualobservationfresides in the requirement for constant operator observationand even then the possibility that. an operator may miss seeing atemporary orifice blockage. Another technique involves the use of RCtiming circuits which involve cut and try settings. The disadvantages ofsuch a technique includejthe temperature sensitivity and agingcharacteristics of RC timing circuits and the number ofadjustments to bemade before an accurate setting may be obtained. An audible method ofblockage detection has 1 also been emp loyedwherein anaudible clickofmechanical or electronic display counters is monitored b the operator.This technique suffersfrorn a number of drawbacks including (1) therequirement for an operator to have a sense of rhythm and (2) thepossibility that an operator who has such a sense of rhythm will miss achange of cadence just as an operator miss seeing orifice blockage inthe aboye-mentionedvisual method. I i A I Still another'blockagedetectiontecliriique involves the generation of a signal in response tonoise dteetion upon obstruction the orifice by rdebris carriedin, asample. This method of detection is generallyinflexible and requires theutilization of critically discriminating noise detection circuitryj v iSUMMARY OF THE iNVENTION The primary object of the present invention isto Another object of the invention is to provide a fl exi ble digitaltimer for measuring sample flow time through an orifice in an electricsensing zone.

Still another object of the invention is to provide a digital timerforsetting a predetermined time operational so that associated articlesize analysis equipment may be operated on'an exactaliquot of materialto per:

tnit normalizing of data. I

According to the inventionfthe foregoing arid other objectives arerealized through theprovision of a digital timing circuit which includes'a clock or time base circuit for deriving Oii'second spaced pulsesfrom a conventional Sit/oi) Hz line waveform. During the timingoperation, these pulses are utilized to drive a register system and attirnesa display counter. In one mode of operation, a norm isdeterminedby reading the elapsed time from the display counter ln a second mode ofopting the register to remember its count and continue counting duringthe manometer resetting process whereby after the monitoring operation,the alarm device is energized in the next 0.1 second to provide avalidating signal as the register continues to count until the mercuryagain clears the start contact andresets the register. This willgenerally sufficeto detect leaks or missetting of the register, butamorecertain detection of these possible conditions is the incorporation ofan additional control gate i on the validating signal" which wouldinhibit such signal if no preset time completion' occurred within, say,0.3 seconds after the mer cury passed from a top to-an unstop level.

Another feature of the invention resides in theprovision of circuitmeans with the flexibility to control or not control the output to apulse height analyzer (FHA) of all particle pulses generated betweenstart and'stop,

or all pulses prior to" stop. I

Another feature of the invention resides in' the fleitibility of thedigital timer wherein the register may be preset'to' a'rnultiple of thepredetermined normal flow time in order to set the sample flow time sothat various sample quantities may be monitored without changing themetered volume of the mercury manometer. In this type of operation,however, the alarm signal is not available to indicate blockage 0rvalidate the opera- 1 .BRI'EF DESCRIPTION OF THE DRAWINGS Otherobjects,'fea tures and advantages of the invention will best beunderstood from the following detailed description taken in conjunctionwith the accompanying drawings, in which:

FIG. l'is a schematic block diagram of a particle sensing zone, acurrent supply to the zone, a pulse height analyzer associatedwith thesensing zone and current supply, and adig ital timer associated with thepulse heightanalyzer and sensing zone apparatus according to theprinciples of the present invention;

FIG. 2 is a schematic logic circuit diagram of a digital timerconstructed in accordance with the principles of the present'inventionfor use in a system such as illustrated in FIG; I; and

FIG. 3 is a schematic logic circuit diagram of the thumb wheel switchassembly illustrated in FIG. 2.

DESCRIPTiON OF THE PREFERRED EMBODIMENT of the same composition as theelectrolyte 11. The ori-,

fice tube 13 includes an orifice 14 for permitting the passage of theelectrolyte 11 containing particles into the interior of the tube 13under the influence of a vacuum.

A current supply 17 is connected to an electrode 15 within the orificetube 13 and to an electrode 16 within the beaker 10 for establishing aflow of current through the electrolyte 11, 12 by way of the orifice 14.As a stream of particles is caused to traverse the orifice 14, eachparticle modulates the current flow to provide a pulse having a heightwhich is representative of its size. These particle pulses are detected,amplified and then analyzed by a pulse analyzer 18.

A mercury manometer is also connected to the vacuum and includes a tube19 having mercury 20 therein which is caused to rise and fall inaccordance with the application of the vacuum to engage and disengage astart contact 21 and a stop contact 22 for controlling the operation ofthe pulse height analyzer 18 during the period of particle sampling.

According to the invention, which will be described in greater detailbelow, a digital timer 23 is provided and connected to the start andstop contacts 21, 22 for monitoring for orifice blockage. The digitaltimer 23 is connected to the pulse counter/size analyzer by way of datalines, symbolically illustrated by the lines 24 and 25, for providinginformation to and receiving information from the pulse counter/sizeanalyzer 18.

Referring to FIG. 2, the manometer 19 with the mercury 20 and the startand stop contacts 21, 22 therein is illustrated in the upper right handcorner of the figure, and the pulse counter/size analyzer 18 isillustrated in the lower right hand corner of the figure. In addition, adisplay counter 80 and a threshhold counter 81 which are portions of thepulse counter/size analyzing apparatus are specifically illustrated inthe lower right hand comer of the circuit.

The major portions of the digital timer illustrated in FIG. 2 are asfollows. A time base in 0.1 second increments is provided from a 50 or60 Hz input by way of a divider 31 which may be, for example, an SN 7490circuit having the gates 32 and 36 associated therewith for resetting.The output of the divider 31 is by way of the conductor 33 and thedivision of the line frequency by five or six is accomplished byselectively connecting either the conductor 35 or the conductor 34 toone input of the gate 32. These conductors are connected to the 12th andninth terminals of the SN 7490 circuit. The sixth, seventh and 10thtenninals of the SN 7490 are connected to ground, the first terminal isconnected to the 12th terminal, the 14th terminal is the trigger input30, the fifth terminal is connected to the supply voltage V, the secondand third terminals are connected to the output of the gate 36, and theeighth terminal is connected to the conductor 33. The 11th terminal isnot used in this particular application.

The 0.1 second time base pulses are supplied by way of the conductor 33and the conductor 37 to a thumb wheel switch assembly 38 which isillustrated in greater detail in FIG. 3.

The thumb wheel switch assembly 38 is utilized for controlling thelighting of the lamp 65 by way of the transistor 69, the diodes 68, 66and the gate 63.

A reset-start switch SW is provided for resetting or starting thedigital timer in conjunction with the position of a function switch FSW.The remainder of the circuit includes a plurality of gates, inverters,and diodes which function in accordance with the settings of theswitches and the position of the mercury with reby way of the conductors33 and 37 to the thumb wheel spect to the start and stop contacts aswill be discussed in detail below.

In FIG. 3, the thumb wheel switch assembly 38 is illustrated ascomprising a plurality of serially connected counters or registers 43,55, 58 having respective trigger inputs 42, 54, 57. These may also be SN7490 circuits connected substantially in the same manner as the divider31 with the exception that the 11th terminal is employed for triggeringthe following stage and/or for encoding purposes by way of therespective thumb wheel switches, such as the switch 52. These switchesmay be of a type available from lnterswitch Corporation and sold underthe assembled switch order code MB-031L-W5. The thumb wheel switches, ascan be seen in FIG. 3, encode their respective counters by 0.1, 1.0 and10.0 second intervals and each includes an output 53, 56, 59 forproviding a preset signal by way of the conductor 39 to the gate 63 forcontrolling the operation of the alarm lamp 65. Encoding is by way ofdiodes, such as the diodes 48-51.

The timer may be set for four different functional operations, asindicated by the four separate positions of the function switch F SW. Inthe fourth position wherein the movable contact FS engages thestationary contact FS4, the count registers of the thumb wheel switchfunction to register the time from start to stop of the mercury meteringsection. This operation should be performed with clean electrolyte and avery clean orifice in order to establish exactly the required time forsample flow. This will hereinafter be referred to as the normal time.With the function switch in the fourth position and with the mercurycolumn depressed, a volumetric run is initiated causing the mercury 20to rise and engage the start contact 21. The gate 92 and the gate 36prevent resetting of the divider 31 and insure an initial reset by wayof the conductor 40 of the counter registers 43, 55, 58. The gate 92,the gate 71 and the inverter 72 control the gate and the inverters 96 topermit pulses shaped by the resistors 27, 28 and the zener diode 29 tobe applied to the trigger input 30 of the divider 31. Accordingly, theline frequency is divided by five or six, as the case may be, andapplied switch assembly for operating the counters 43, 55, 58. At thesame time, the ground potential applied to the switch terminal FS4 hascaused the gate 76 to be primed for operation by way of the diode 84 andthe inverter 86, and the output pulses of the divider 31 are registeredin a display counter by way of the gate 76 and the inverter 79. During arun in the fourth position, the thumb wheel switch assembly has thethumb wheel switches 52, 56, 59 set to a value much higher than thatexpected to be counted in order to prevent the occurence of an alarm;otherwise, the alarm lamp may be ignored during the run.

As the mercury 20 rises and engages the stop contact 22, the gate 71 andthe inverter 72 operate to cause the gate 95 and the inverter 96 toprevent the application of the line derived pulses to the divider 31. Itshould be noted that in position F84, the function switch FSW controlsthe gate 94 so as to prevent the application of any output to the FHA18.

As the mercury 20 is again depressed and disengages the contact 22 andthen the contact 21, the gate 71 and the inverter 72 again cause thegate 95 and the inverter input 30 of the divider 3 l and the gate 92permits resetting of the divider by way of gate 36 (and the gate 32).:

With the switch PSW having its contact .PS connected to its contact PS1,and with the thumb wheel switches set to the time measured in theposition PS4 plus 0.1 seconds, a runwith-particles suspended in theelectrolyte 11 maybe made. Again, as the mercury engages the startcontact 21, the gate92 prevents resetting of the divider by way of thegate. 36 and the gate 71 and the inverter 72 cause the gate,95 and theinverter 96 to permit the application oftrigger pulses to the triggerinput 30 of the diyider 31. The 0.1 second spaced pulses appear at theoutput conductor 33 and are extended by way of the conductor 37 to thethumb wheel switch assembly 38. Inasmuch as noground signal is appliedto the inverter 86 or to the inverter 87, the gate 76 will beineffective to' gate the pulses to the display counter 80';therefore','th 'display counterwill not be exercise d for avisual'display' of elapsed time; however, the gates and diodes 93, 71-73and 77 via the conductor 75 permit all particle pulses from the'thr'eshold circuit 81 to be counted prior to stop. As the "triercury 20 engagesthe stop contact 22, the line pulses are again prevented from operatingthe divider 31 by virtue of the elements 71, 72, 95, 96 and the 0.1second spaced pulses will not be generated. Therefore, if the lamp 65has not been energized, the run has taken less time than that encoded inthe counters 43, 55, 57 by the thumb wheel switches. If, however, thelamp 65 has been energized, such would occur by way of the outputconductors 53, 56, 59 of the thumb wheel switches to extend a signalover the conductor 39 to the gate 63. The gate 63 and the resistor 67connected to the supply voltage V reverse bias the diode 66 and cause aforward biasing of the diode 68 to render the transistor 69 conductive.

Assuming that the run was performed within the time set on the thumbwheel switches, and that the mercury is caused to be depressed to clearthe stop contact 22 and then the start contact 21, first the gate 71 andthe inverter 72 cause the gate 95 and the inverter 96 to permit theprovision of the time base pulses on the conductor 33. The counters 43,55, 58 remember the time to which they were exercised during the run andcontinue to count upwardly from that time until the mercury clears thestart contact 21 causing resetting of the divider at the gates 32, 36.The continued running of the counters 43, 55, 58 will cause the count torise above that preset by the thumb wheel switches so that the conductor39 is provided with a potential for causing the gate 63, the diodes 66,68, the resistor 67 and the transistor 69 to energize the lamp 65. Thissignal is only momentary and causes the lamp to flash thereby providinga validating signal that the circuit has functioned properly during theprevious run.

With the function switch PSW having its contact PS engaged with itscontact PS2, the same functions apply as in the position PS1 except thatthe signal output is present only when the mercury is between the startand stop contacts (gates 74, 94). This permits size analysis apparatusto be operated on an exact aliquot of material as a normalizer for data.

With the function switch contact PS engaging the contact PS3, themercury contacts no longer control the register start-stop, and insteadthe timer preset value determines how long the particles will beregistered. Thus, one would simply leave the vacuum valve open and pushthe switch SW for resetting the thumb wheel switch assembly whereby uponrelease, counting will proceed for the preset time. This allows datanormalizing on a preset time basis, which in itself may not be oftremendous value; but which also allows one to preset a time that issome multiple of the time measured in position PS4 so that differentquantities may be counted without changing the mercury volume section ofthe apparatus. During such a run which effectively changes theoperational test time, one of the prior art methods, such as visualobservation, should be employed to guard against false results uponblockage of the orifice. I I

The start contact 21 and the stop contact 22 are connected to controlthe gate 71 whereby a gate 74 may be operated to provide a gating pulseto the apparatus 18, which pulse has a width equal to the travel time ofthe mercury between the contacts 21, 22. In the position 4, such a pulsedoes not occur and theinput to the apparatus 18 is placed at a constantpotential inasmuchv as in this position particle pulses may not begenerated at all if there is a clean electrolyte.

The threshold circuit 81 responds to particle pulses generated during anoperational run and provides indications of such pulses to the gate 77which extends these pulses to the display counter 80 by way of theinverter 79 in accordance with positions PS2 and PS3 of the functionswitch. The gate 77 is controlled by way of the conductor connected toan input of the gate 74. The gate 74 is controlled over a diode 73 byway of the inverter 72 and the gate 71, and this circuit is in turncontrolled by the start and stop contacts 21, 22. Therefore, accordingto which position PSI-PS3 the switch FSW is in, particle pulses betweenstart and stop, or all particle pulses before stop, may be registered onthe display counter.

In the embodiment of the invention illustrated in the drawings, thegates and inverters were realized by well known 930, 936 and 946circuits.

Although I have described my invention by reference to a specificillustrative embodiment thereof, many changes and modifications maybecome apparent to those skilled in the art without departing from thespirit and scope of the invention, and it is to be understood that Iintend to include within the patent warranted hereon all such changesand modifications as may reasonably and properly be included within thescope of my contribution to the art.

I claim:

1. In an apparatus for monitoring the flow rate in a particle analysissystem of the type including an orifice tube having an orifice anddisposed in an electrolyte and connected in fluid communication with avacuum source, a mercury manometer also connected to the vacuum sourceand having a pair of spaced start and stop electrodes to be sequentiallyengaged and disengaged by the mercury upon application and release ofthe vacuum, and means for sensing particle flow through the orifice andproviding particle pulses in response thereto to particle counting andanalyzing equipment, the improvement therein of means for performing atest runwith a clean electrolyte and a clean orifice followed by atleast one operational run with an electrolyte having particles suspendedtherein comprismg:

clock means operable to produce clock pulses;

means for setting said counting means after a test run to apredetermined time count in accordance with the count displayed for thetest run; and alarm means connected to said counting means and operatedduring an operational run to indicate time counts greater than thepredetermined time. 2. Apparatus according to claim 1, wherein saidalarm means comprises an indicator lamp.

3. Apparatus according to claim 1, wherein said alarm means includes alamp connected to said counting display means.

4. Apparatus according to claim 1, wherein said means for setting saidcounting display means comprises:

switch means connected to said counting means and operable to presetsaid counting means, said switch means including indicia means forproviding a visual indicia of the time setting.

5. The apparatus according to claim I, wherein said clock meanscomprises:

means for connection to an alternating wave electrical supply andoperable to shape the wave thereof into pulses having the same periodicoccurrence;

and

a frequency divider connected to said shaping means to divide thefrequency of the shaped wave.

6. The apparatus according to claim 5, wherein said frequency dividerincludes means operable to provide 0.1 second spaced pulses from theinput pulse fre quency.

1. In an apparatus for monitoring the flow rate in a particle analysissystem of the type including an orifice tube having an orifice anddisposed in an electrolyte and connected in fluid communication with avacuum source, a mercury manometer also connected to the vacuum sourceand having a pair of spaced start and stop electrodes to be sequentiallyengaged and disengaged by the mercury upon application and release ofthe vacuum, and means for sensing particle flow through the orifice andproviding particle pulses in response thereto to particle counting andanalyzing equipment, the improvement therein of means for performing atest run with a clean electrolyte and a clean orifice followed by atleast one operational run with an electrolyte having particles suspendedtherein comprising: clock means operable to produce clock pulses;counting means responsive to the clock pulses including counting displaymeans for displaying pulse counts; means connecting said counting meansto said clock means; means for selectively connecting said display meansto said clock means or the sensing means to display pulse count as time,or display the traversing of particles through the orifice,respectively; control means connected between the start and stopelectrodes and said clock means for controlling the production of clockpulses; means for setting said counting means after a test run to apredetermined time count in accordance with the count displayed for thetest run; and alarm means connected to said counting means and operatedduring an operational run to indicate time counts greater than thepredetermined time.
 2. Apparatus according to claim 1, wherein saidalarm means comprises an indicator lamp.
 3. Apparatus according to claim1, wherein said alarm means includes a lamp connected to said countingdisplay means.
 4. Apparatus according to claim 1, wherein said means forsetting said counting display means comprises: switch means connected tosaid counting means and operable to preset said counting means, saidswitch means including indicia means for providing a visual indicia ofthe time setting.
 5. The apparatus according to claim 1, wherein saidclock means comprises: means for connection to an alternating waveelectrical supply and operable to shape the wave thereof into pulseshaving the same periodic occurrence; and a frequency divider connectedto said shaping means to divide the frequency of the shaped wave.
 6. Theapparatus according to claim 5, wherein said frequency divider includesmeans operable to provide 0.1 second spaced pulses from the input pulsefrequency.